/* dualview.c --  为字段和按位运算符 */
#include <stdio.h>
#include <stdbool.h>    //  C99 定义了 bool、true、 false
#include <limits.h>

/* 位字段符号常量 */
/* 边框线样式 */
#define SOLID   0
#define DOTTED  1
#define DASHED  2
/* 三原色 */
#define BLUE    4
#define GREEN   2
#define RED     1
/* 混合色 */
#define BLACK   0
#define YELLOW  (RED | GREEN)
#define MAGENTA (RED | BLUE)
#define CYAN    (GREEN | BLUE)
#define WHITE   (RED | GREEN | BLUE)

/* 按位方法中用到的符合常量 */
#define OPAQUE          0x1
#define FILL_BLUE       0x8
#define FILL_GREEN      0x4
#define FILL_RED        0x2
#define FILL_MASK       0xE
#define BORDER          0x100
#define BORDER_BLUE     0x800
#define BORDER_GREEN    0x400
#define BORDER_RED      0x200
#define BORDER_MASK     0xE00
#define B_SOLID         0x0
#define B_DOTTED        0x1000
#define B_DASHED        0x2000
#define STYLE_MASK      0x3000

const char * colors[8] = {"black", "red", "green", "yellow",
"blue", "magenta", "cyan", "white"};

struct box_props
{
    bool opaque                 : 1;   //  或者 unsigned int (C99以前)
    unsigned int fill_color     : 3;
    unsigned int                : 4;
    bool show_border            : 1;   //  或者 unsigned int (C99以前)
    unsigned int border_color   : 3;
    unsigned int border_style   : 2;
    unsigned int                : 2;
};

union Views     /* 把数据看作结构或 unsigned short 类型的变量 */
{
    struct box_props st_view;
    unsigned short us_view;
};

void show_settings(const struct box_props * pb);
void show_settings1(unsigned short);
char * itobs(int n, char * ps);

int main(void)
{
    /* 创建Views, 并初始化 initialize struct box view */
    union Views box = { {true, YELLOW, true, GREEN, DASHED} };
    char bin_str[8 * sizeof(unsigned int) + 1];

    printf("Qriqinal box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);

    printf("bits are %s\n", itobs(box.us_view, bin_str));
    box.us_view &= ~FILL_MASK;                  /* 把表示填充色的位清0 */
    box.us_view |= (FILL_BLUE | FILL_GREEN);    /* 重置填充色 */
    box.us_view ^= OPAQUE;                      /* 切换是否透明的位 */
    box.us_view |= BORDER_RED;                  /* 错误的方法 */
    box.us_view &= ~STYLE_MASK;                 /* 把样式的位清0 */
    box.us_view |= B_DOTTED;                    /* 把样式设置为点 */
    printf("\nModified box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);
    printf("bits are %s\n", itobs(box.us_view, bin_str));

    return 0;
}

void show_settings(const struct box_props * pb)
{
    printf("Box is %s.\n",
        pb->opaque == true ? "opaque" : "transparent");
    printf("The fill color is %s.\n", colors[pb->fill_color]);
    printf("Border %s.\n",
        pb->show_border == true ? "shown" : "not shown");
    printf("The border color is %s.\n", colors[pb->border_color]);
    printf("The border style is ");
    switch (pb->border_style)
    {
    case SOLID:
        printf("solid.\n");
        break;
    case DOTTED:
        printf("dotted.\n");
        break;
    case DASHED:
        printf("dashed.\n");
        break;
    default:
        printf("unknown type.\n");
        break;
    }
}

void show_settings1(unsigned short us)
{
    printf("box is %s.\n", (us & OPAQUE) == OPAQUE ? "opaque" : "transparent");
    printf("The fill color is %s.\n", colors[(us >> 1) & 07]);
    printf("Border %s.\n", (us & BORDER) == BORDER ? "shown" : "not shown");
    printf("The border style is ");
    switch (us & STYLE_MASK)
    {
    case B_SOLID:
        printf("solid.\n");
        break;
    case B_DOTTED:
        printf("dotted.\n");
        break;
    case B_DASHED:
        printf("dashed.\n");
        break;    
    default:
        printf("unknown type.\n");
        break;
    }
    printf("The border color is %s.\n", colors[(us >> 9) & 07]);
}

char * itobs(int n, char * ps)
{
    int i;
    const static int size = CHAR_BIT * sizeof(int);

    for (i = size - 1; i >= 0; i--, n >>= 1)
        ps[i] = (01 & n) + '0';
    ps[size] = '0';

    return ps;    
}